Method of manufacture

ABSTRACT

A tubular aluminum member is extruded in a rectangular shape and cut to a given length. The four walls of the tubular member are successively cut by a circular saw to form a portion of the tubular member into a generally spiral shape winding with terminal portions at each end. The member is treated to form an insulating layer on the surfaces of the member including the facing sides of the winding to form an inductive winding for passing current. The winding may be compressed and one set of edges treated for engagement by current taps to produce a variable voltage and current device.

United States Patent Davis [15] 3,656,378 Apr. 18,1972

[54] METHOD OF MANUFACTURE 21 Appl.No.: 99,110 I Related US. ApplicationData [62] Division of Ser. No. 784,979, Nov. 12, 1968, aban- UNITEDSTATES PATENTS 2,370,265 2/1945 Shoemaker ..29/2 .2 X

3,466,743 9/1969 De Puy ..29/602 Primw Examiner-James M. MeisterAttorney-George C. Bower [5 7] ABSTRACT A tubular aluminum member isextruded in a rectangular shape and cut to a given length; The fourwalls of the tubular member are successively cut by a circular saw toform a portion of the tubular member into a generally spiral shapewinding with terminal portions at each end. The member is treated toform an insulatinglayer on the surfaces of the member including thefacing sides of the winding to form an inductive winding for passingcurrent. The winding may be compressed and one set of edges treated forengagement by current taps to produce a variable voltage and currentdevice.

10 Claims, 20 Drawing Figures PATENTEDAPR 18mg SHEET 2 [IF 5 PATENTEDAPR18 I972 SHEET 3 BF 5 "INVENTOR.

47 55 I Z3 44 62 flew/3 v Anne/v0 BACKGROUND OF THE INVENTION The usualmethod of forming inductive windings is to wrap cylindrical copper wirearound a core. Inductive windings have also been formed by interleavingsheet metal strips with insulating pieces to form an inductive windingor bending continuous metal ribbon into inductive turns. The standardcylindrical wire type of winding has problems of heat dissipationthrough the layers of turns and corrosion and pitting of the wire onengagement by a variable voltage tap. The stacked laminations of sheetmetal and insulating pieces requires the transfer of current betweenengaging surfaces of the laminations. The distortion of an edge bentmetal ribbon to form an inductive winding is not satisfactory. All ofthe foregoing forms have an additional disadvantage of transference ofload current across connections. Such connections are a source ofmaintenance problems.

SUMMARY OF THE INVENTION An inductive winding is formed from a tubularmember by cutting around the wall of the tubular member to formcontinuous turns of a winding with terminal portions at each end so thatcurrent is passed from the terminal portions through the windingswithout transferring between two engaging surfaces.

An object of the invention is to provide a single piece inductivewinding that has flat side surfaces between and on the turns.

Another object of the invention is to provide an inductive winding withterminal portions that are formed with the inductive winding as a singlepiece.

Another object of the invention is to provide an inductive winding thatpasses current without transfer between surfaces and conducts heatthrough the side surfaces of the winding.

Another object of the invention is to provide an inductive winding and aheat sink as a single piece of metal.

Another object of the invention is to provide as a single piece aninductive winding and a component supporting member in electricalconductive relation with the winding and support member.

Other and further objects and advantages will be apparent from thefollowing description taken in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 perspectively illustrates anuncut tubular member with exterior smooth surfaces.

FIG. 2 perspectively illustrates an uncut tubular member with exteriorfins on three surfaces. 2

FIG. 3 perspectively illustrates the exterior smooth surface tubularmember with winding cut therein.

FIG. 4 perspectively illustrates a finned tubular member with the finsremoved from a section and a winding formed therein.

FIG. 5 perspectively illustrates a finned tubular member with thewinding section having fins.

FIG. 6 illustrates the smooth side of the finned tubular member withnotches for passing an iron core member.

FIG. 7 is a view of one of the sides illustrating cuts forming thewinding.

FIG. 8 illustrates a surface adjacent to the surface shown in FIG. 7.

FIG. 9 illustrates the turns of the winding spaced.

FIG. 10 is a fragmentary perspective view of the turns of the winding.

FIGS. 11 and 12 illustrate the cutting of the wall of the tubular memberby a circular saw.

FIG. 13 fragmentarily illustrates a toroidal winding.

FIGS. 14a through d diagrammatically illustrate the fragments of thesides of the uncompressed toroidal winding.

FIG. 15 is a diagrammatic view illustrating the relationship of thetubular member and the circular saw.

FIG. 16 is a fragmentary sectional view of a winding with a plurality ofvariable contacts.

FIG. 17 illustrates a transformer with a cordance with the invention.

DETAILED DESCRIPTION Referring to FIG. 1 of the drawings, a tubularmember 20 is illustrated having a bore 21 extending longitudinallytherethrough and of a generally square configuration formed by walls 22,23, 24, 25. The tubular member may be made of aluminum and extrudedthrough a die with a floating mandrel using a hollow aluminum billet.The aluminum may be 6063 or EC grade with a T6 temper for bestmachiningqualities. The tubular member is cut in any desired length from theextrusion. The exterior surfaces of the walls may be smooth or, asillustrated in FIG. 2, have cooling fins 26, 27, 28 extendinglongitudinal to the member and perpendicular to the walls 22, 23, 25.The exterior surface of wall 24 is smooth. The walls of the tubularmember are cut as described later herein to form a winding 35 withterminal portions 36, 37 at each end as illustrated in FIG. 3.

The fins may be removed (FIG. 4) from a portion of the member to form awinding section 30 with flat sides 22 to 25 and a heat sink section 31with cooling fins 26, 27, 28. The winding section 30 with the flat sidesmay be cut in accordance with the method of this invention to form aninductive winding 32 while the heat sink section 31 supports electricalcomponents (not shown). In the embodiment of FIG. 5 the winding 38 iscut in the finned embodiment of FIG. 2 without removing the fins fromthe winding section, so that the winding 38 has fins 26, 27, 28.

The tubular member 20 or winding section 30 has longitudinal cuts 40, 41in the smooth exter wall 24 (FIG. 7) immediately adjacent to theopposite walls for forming notches 50, 51 in the side for subsequentlyreceiving an iron core. A longitudinally extending bore 42 may be cut inone of the walls for receiving a terminal prong 39 threaded therein.

The winding or coil 35 is cut in the tubular member 20 by fitting thetubular member in a vise or clamping members 43, 44 (FIGS. 11 and 12)and moving a circular rotating saw 45 downwardly through the upper side22 of the tubular member. The circular saw 45 (FIGS. 11, 12) isperpendicular to the side 22 to be cut and centered in relation to thesides 23 and 25 The axis A (FIG. 15) of the saw is at a slight angle toplane B extending longitudinally midway between the sides 23, 25 andperpendicular to the side 24. The center point of the saw is in thisplane B. The saw has a diameter so that the periphery of the saw cutseach of the inner and outer corners 46, 47, 48, 49 of a side at the sametime. This is best illustrated by the curved line 56 between corners 46,47 (FIG. 12). The member is then removed from the vise or clampingmembers and rotated to present side 23 for cutting (FIG. 11). The planeB extends longitudinally midway between the sides 22, 24 andperpendicular to side 25 The axis A of the saw is at a slight angle withthe centerpoint of the saw in the plane. The tubular member ispositioned so that on completion of the cut in this side the saw is inline with the portion of the previous cut 50 inside 22. The cut 50 iscontinuous through successive sides. Instead of a single saw being used,multiple saws may make all cuts in one wall of the tubular member at thesame time. Thus by four successive positions of the tubular member theentire winding can be formed. The first and last cuts on the wall 24intersect the longitudinal slots 40, 41 to form the slots 51, 52 for theiron core.

As seen from the fragmentary views of the winding in FIGS. 9 and 10 thesuccessive angular cuts in the walls 22, 23, 24 and 25 produce arectangular shaped winding with a continuous space 50 between the turns.The winding in this form is resilient and may be compressed so that theside surfaces 53 and 54 in the wall 22, side surfaces 55, 56 in the wall23, side winding in acsurfaces 57, 58 in the wall 24 and side surfaces59, 60 in the wall 25 are in engagement. A thin insulating coating,later described herein, is provided on these sides to isolate the turnsand form the winding into an inductive winding. Thus the side surfacesmay be compressed in a close contiguity for transfer of heattherebetween.

The tubular member with the winding 35 and the terminal portions 36, 37may be heat treated and annealed to a soft temper to increase theconductivity of the metal. The tubular member can then be furthertreated to form an insulating coating on the surface of the tubularmember and particularly the facing sides 53, 54 of the winding. Also,the facing sides 55, 56; 57, 58 and 59, 60 require an insulatingcoating. The fins are also treated. The coating also improves theradiation properties of the tubular member and various colors may beprovided depending upon the desired appearance. The anodized coating onthe side walls of the winding permits the winding to be pressed togetherwithout shorting the windings while permitting substantial heat flowbetween the surfaces to provide a short heat path for removal of theheat from the windings.

An insulating coating may also be provided by covering the tubularmember with an epoxy cement containing glass spheres of 0.004 in. to0.005 in. in diameter. The insulating glass spheres maintain a minimumspacing between the windings so that the side surfaces of the windingshave a layer of epoxy therebetween. The glass spheres act as spacerswhen the coils of the winding are forced together and prevent theextrusion of the epoxy and a metal to metal contact between thewindings. Thus an adequate insulating is provided between the turns.

Additional coating may be provided on the exterior surfaces of thetubular member and fins by spraying an epoxy on the surface or byheating the tubular member and placing it into a bed of epoxy powder.This may be done on an anodized tubular member and an unanodized tubularmember.

In the coating process masks may be applied to the metal surfaces atdesired areas where electrical contact with the metal is desired.

The winding may be held in a compressed condition by an insulating plate61 being positioned along one of the sides of the tubular member 20 orwinding sections 30 or winding 38 and fastened to the terminal portionsat each end. The insulating plate 61 has matching notches. The tubularmember with the winding may be used in various embodiments. For example,a primary winding may be used in various embodiments. For example, aprimary winding 62 (FIG. 17) may be positioned around the outside of thetubular member and an iron core 63 fitted in the bore. The iron core maybe made of U- shaped silicon steel straps or be made of a tape woundcore cut into U shapes or may be powdered iron or powdered ferritemoulded into U shapes. The U shapes each have a leg inserted into thebore 21. The ends of the bore may be closed by plates 66 and the borefilled with rubber, flexible urethane, flexible rubber, silicon rubberor the like and solidified by a catalyst or heating to support the ironcore and electrically isolate it from the winding. The elastomer assistsin absorbing noise that may be caused by vibrations of the iron core.The winding sections 30 and 38 also have an insulating plate 61 and aniron core 63.

The legs of the two U-shaped pieces 64, 65 may be in contact or may bespaced, depending upon the characteristics to be imparted to theassembled unit. A mica spacer 67 may be positioned between the ends ofthe legs. Cores with a small air gap may be used to provide linearreactors. The gap between the cores can be adjusted depending upon thelinearity of saturation of the core that is desired. This will dependupon the use of the device. The tubular member with the winding isparticularly useful where high load currents are passed by the winding.Such load currents occur in chokes used in series with solid statecontrolled devices, in rectifier power supplies, in adjustableautotransformers, dimmer and magnetic amplifiers, linear reactors andthe like.

For solid state controlled devices the tubular member with heat sink 31(FIG. 4) is used. The solid state controlled devices are mounted in theheat sinks. Thus the heavy currents passed by the solid state controlleddevices are conducting through the terminal portions, winding, into theheat sink with the current passing only through the surfaces betweensurfaces of the heat sink and solid state controlled devices. Thisgreatly reduces the factors that create heat and also provides a readydissipation of any heat created by the same element that is carrying theheat.

In FIG. 16 a fragmentary sectional view of an adjustableautotransforrner 70 having a plurality of variable contacts 71 engagingthe turns of the winding 72 is shown. The winding has an insulatingcoating 73 of anodized aluminum or epoxy resin. The U-shaped members 74,75 of the iron core choke are in engagement at 76 and potted in siliconrubber 77. The turns of the aluminum winding 72 have a conductiveresistive coating 78, such as Nichrome. The brushes 71 engage thesecoatings and provide a resistance to circulating currents throughbridged windings and a contact 71. The contact 71 may be made of anysuitable material, such as carbon.

The tubular member with the winding and terminal portions, including theembodiments with the heat sinks and fins, may be utilized in manydifierent types of apparatus of which the foregoing are onlyillustrative.

In FIGS. 13 and 14 a toroidal winding 35a is fragmentarily illustratedand embodies the principles of the invention. The tubular member 20a haswalls 22a to 25a. The walls 220 and 24a are cut as shown in FIGS. 14band d. The walls 22a and 240 have pie or V-shaped cuts 220 and 240between the winding segments 22b and 24b, respectively. The cuts may bemade by positioning the axis of the saw shaft at an angle A on one sideof plane B and then at an angle A on the other side of plane B. The pieshaped cuts in the wall 24a are similarly formed with the narrowportions at the wall 23a. The wall 230 has the narrow segments 23b andthe wall 25a has the broad segments 25b formed by the cuts 230 and 250at an angle C to the plane B. The winding compresses into a'circularconfiguration as partially illustrated in FIG. 13. The tapered segments22b and 24b are normal to the sides 23a and 25a on cutting and assume aradial position on compression. The general spiral configuration to forman inductive winding is attained by the slope of the segments 23b and25b. As illustrated in FIGS. 14a and 14b the angle C is greater thanangle A. The segments are arranged in FIGS. 14a and b with contactingends adjacent in the figures to illustrate the progression of thewinding. The surface of the winding may be treated as in the otherembodiments to provide an insulating coating by anodization orpolymerization of a resin. The surfaces 22a may be provided with asurface similar to the embodiment of FIG. 16 for engagement by movablecontact means to tap a range of voltages and currents.

It is thus seen from the foregoing description that a new type ofinductive winding and method of manufacture of an inductive winding havebeen provided. The winding may be formed by machinery and may beautomated. The tubular member is readily extruded and the winding cut toprecise dimensions rapidly by multiple circular saws. The insulatingsurfaces on the winding may be readily produced by standard anodyzingprocesses.

The winding has the particular feature that the winding and terminalportions are a single piece without any current transferring surfaces orconnections. Also, the individual turns are flat rectangular pieces withconsiderable depth normal to the exterior surfaces of the winding andwith extended transverse facing surfaces for the transference of heatlongitudinally along the winding. This is particularly advantageous whenvariable contacts engage the outer surfaces of the windings for tappingvarious voltages or currents therefrom. Heat produced between thecontact and the winding is carried inwardly and longitudinally fordissipation, thus reducing or preventing the pitting or corrosion of theengaging surfaces. Further, the winding may be readily provided withcooling fins '5 and may be formed as a single piece with a heat sink fordissipation of heat developed in the winding. Further, the heat sink maybe used to support other heat generating electrical components whichwill be in electrical conductive relation with the winding by atransference of current through a single contacting surface. Thus theamount of heat generated is greatly reduced and the heat that isgenerated may be readily dissipated. Therefore, an inductive windingwith heat dissipating means may be readily manufactured by machinemethods which has good heat dissipating and current transferringcharacteristics.

Various modifications and changes may be made in the various embodimentswithout departing from the invention as set forth in the appendedclaims.

Iclaim:

1. A method of manufacturing an inductive winding from a generallyrectangular, tubular, electrically conductive member havinglongitudinally extending walls with longitudinally extending inner andouter surfaces and longitudinally extending inner and outer cornersjoining longitudinally adjacent inner and outer surfaces comprisingcutting through each wall from the respective outer surface to therespective inner surface and to the respective corners to form seriallyconnecting generally spiral-liketurns in inductive relation.

2. A method of manufacture as set forth in claim 1 wherein an insulationis provided between said turns.

3. A method of manufacture as set forth in claim 1 wherein said step ofcutting is a slight angle to the normal of the lon- 6 gitudinal axis.

4. A method manufacture as set forth in claim 1 wherein the step ofcutting a wall is by circular saw means.

5. A method of manufacture as set forth in claim 1 wherein the step ofcutting is from the longitudinal center area of an outer surface of awall to the longitudinal center area of the respective inner surface andthe center areas to each of the respective inner and outer corners alongthe wall being cut.

6. A method of manufacture as set forth in claim 1 wherein the step ofcutting of a wall is by a plurality of circular saws rotating about anaxis at a slight angle to the longitudinal axis of the winding andsimultaneously cutting a given wall.

7. A method manufacture as set forth in claim 1 wherein the step ofcutting is through successive walls.

8. A method of manufacture as set forth in claim 1 wherein the step ofcutting is by a circular saw having a radius to intersect the inner andouter corners and rotating about an axis at a slight angle to thelongitudinal axis of said member.

9. A method of manufacture as set forth in claim 8 wherein in the stepof cutting the inner and outer comers are intersected simultaneously.

10. A method of manufacture as set forth in claim 1 wherein the step ofcutting is the successive cutting of the walls by a plurality ofparallel and simultaneous cuts at a slight angle to the normal of thelongitudinal axis of the tubular member and each cut simultaneouslyintersecting the inner and outer corners.

1. A method of manufacturing an inductive winding from a generallyrectangular, tubular, electrically conductive member havinglongitudinally extending walls with longitudinally extending inner andouter surfaces and longitudinally extending inner and outer cornersjoining longitudinally adjacent inner and outer surfaces comprisingcutting through each wall from the respective outer surface to therespective inner surface and to the respective corners to form seriallyconnecting generally spiral-like turns in inductive relation.
 2. Amethod of manufacture as set forth in claim 1 wherein an insulation isprovided between said turns.
 3. A method of manufacture as set forth inclaim 1 wherein said step of cutting is a slight angle to the normal ofthe longitudinal axis.
 4. A method of manufacture as set forth in claim1 wherein the step of cutting a wall is by circular saw means.
 5. Amethod of manufacture as set forth in claim 1 wherein the step ofcutting is from the longitudinal center area of an outer surface of awall to the longitudinal center area of the respective inner surface andthe center areas to each of the respective inner and outer corners alongthe wall being cut.
 6. A method of manufacture as set forth in claim 1wherein the step of cutting of a wall is by a plurality of circular sawsrotating about an axis at a slight angle to the longitudinal axis of thewinding and simultaneously cutting a given wall.
 7. A method ofmanufacture as set forth in claim 1 wherein the step of cutting isthrough successive walls.
 8. A method of manufacture as set forth inclaim 1 wherein the step of cutting is by a circular saw having a radiusto intersect the inner and outer corners and rotating about an axis at aslight angle to the longitudinal axis of said membEr.
 9. A method ofmanufacture as set forth in claim 8 wherein in the step of cutting theinner and outer corners are intersected simultaneously.
 10. A method ofmanufacture as set forth in claim 1 wherein the step of cutting is thesuccessive cutting of the walls by a plurality of parallel andsimultaneous cuts at a slight angle to the normal of the longitudinalaxis of the tubular member and each cut simultaneously intersecting theinner and outer corners.